Computing devices often request content from other computing devices over a network. In a common application, the computing device operated by a requesting user is referred to as the client, and the computing device or system operated by the content provider that responds to the request is the server. A client and server may communicate over an intranet, the Internet, or any other communication network. Content providers often reserve areas of their content for advertisements. Advertisers can purchase the available space, referred to as inventory, to display their advertisements. Advertisers and content providers typically employ an advertisement server or an advertising network of servers to facilitate the sale of inventory and the distribution of advertisements.
Clients receive and process content (e.g., web pages) from content servers, and then retrieve and process advertisements associated with the content from an advertisement server. The retrieval and processing of the advertisements may cause a user of the client to experience delays and performance degradation due to the retrieval of the advertisement in addition to or after the retrieval and initial processing of the requested content. Moreover, when a user of a client is browsing content offline, advertisements associated with the content may not be available, resulting in unused inventory for content providers and lost advertising opportunities for advertisers.